Pump pressure control system



Oct., 22, 1946. R R CURTlS PUMP PRESSURE CONTROL SYSTEM Filed March 6, 1943 Patented oct. 22, 1946 PUMPPRESSURE CONTROLISYSTEM Russell R. Curtis, Dayton, Ohio, assignorto Curtis.-

Pump Company, Dayton, Ohio, a corporation of Y Ohio `lipplimtin March 6, 1943,*ser'ia1'Nq.-478,213

Claims.

This invention relates to the maintenance of selected pump `pressure differentials above selected base pressures. Y,

Specifically the invention relates to the-control of-fpump discharge pressures'by a rstbalanced relief valve assembly ,subjected` to pump .pressure on one side `and base pressure-.onlthe otherside, together with Va positively-controlled valve for subjecting the balanced relief valveassembly to pump discharge pressure instead of said base pressure, and a secondrelief valve assembly for limiting the effect of `pump pressure on said first relief valve assembly-whereby the .pump candeliver fluid under selectedconstant pressuredifferentialsi-based on the same Aor .different base pressures. Y

.This invention is especially `applicableto aircraft fuel systems and Iwill lhereinafter `be described as 4embodied .in such systems, `although it should be understood that the .invention Ais Vnot limited to aircraft usage. According to this invention, a. fuel .pump with a balancedrelief 'valvefassemblyismountedrin an airplane fuel tank to receivefuel therefrom rand deliver the fuel underpressure througnafuelline to asecondiuelpump .driven by the airplaneengine. The fuel pumpin the tank is ,preferably driven by an electric motor. i I The fuelpump S in .the .tankig equipped with: a spring-urged relief valve setto .maintain a desired. pressure on `the ,dischargeside of the pump, inthe order of seven oreighttpoundspersquare inch. "Such pressures will prevent liberation of gases and vapors",inrthefuelline- In order to 'maintain a constant-,pressure differential. inthe discharge side ofjthe fuel' pump, determined solely bythe springjpressure rexerted on-.the relief valve of'this pump, .a diaphragmlis provided in the Arelief valve assembly which is subjected to pump pressure `on .one sidel and "basel, pressure on the othergside during" normal operation. The basei pressureis lpreferably that pressure existing in the' tank in' `Whichthe 'fuel pump is' mounted.

"Under emergency Aconditions, as,.for example, inhigh altitudeiyingyand in case'of damage to the engine-driven `ifuerpump, it"`is desirable .to maintain a higher pressure differential on 'theldischarge-sideof the pump mounted in 'the tank. For this purpose, the discharge sid'eof i:the pump is joined `with a*positively-controlled valve such as -asolenoidioperated =valve. When this valve Vis actuated it Willsulojec't 4"both sides of the-relief valve to pump discharge pressures insteadofsubjecting onellside ``to pump discharge pressure and the/other sidetofbasejpressure-las in normal operation. 'A-second relief valve 4isalso providedto limitthe pump `discharge pressure---eect on the balancing :means of theipumplrelief Valve. "This second? `relief valve 4"is subjected toibase'r'pressure on'loneside .fandpump l discharge pressure 'on the otherside. A spring in thistsecond relief-valve Will `determine .the pressureadifferential maintained by the .pump under emergency dutyperformance. Y. Y

V'The .system of this invention ythus providesffor the maintenance `of 'selected pump pressure :differentials, based on the same or .diiferent Abase pressures.` For example, Hthebalancing rmeans of theV pump relief valve canbe subjected -tofa ibase pressuresuch-.as existsvin the fuel tank, while the Second `relief Valve can be subjected .to-.1a `base pressure such as existsin thefueltanhorthe supercharger pressureof the airplane engine [being suppliedfby thepump.

fI-t is, fthen, an object Aof this invention `to provide .an assembly for maintaining ,selectedt pressure differentials based .on-the sameiorfdifferent base pressures. i,

`Afurther object `ofthe ',inven'tion Lis topr videa pump assembly having a 4balanced relief valveiwith a Vrelief valve` contrlsystem sci that' the pump can maintain different selected I'discharge pressures. i

Astill further object of {theinvention .isjto providefan aircraft fuel` systemcapable of ,delivering a'constantnormal fuel pressure differential above albasefpressure as Wellas a constant increased emergency" fuel pressure .diferentialfabove a'bfase pressure. Y

A still 'further objectief theinvention is .to provide, `in an aircraft `fuel system 'havinga plurality of fuel pumps in seriesortandem arrangement, a' relief valvearrangement for at leastone ofsaid pumps capable ofV automatically maintainingfdifferent selected fuelpressures.

VAnotheriobject istoprovidefa positivedisplacement type booster pump for aV fuel system witha relief valve assembly that can `be selectively controlledto maintain a selectedjconstant pressure differential on"`the discharge 'side of the (booster pump above a selected basejpressure.

A `still further obj ectofY this inventionjis to-Lpro- Videg'inian aircraft fuel systemjof the booster pumpeengine-driven fuel pump type, a'positiv'edisplacement booster pumphaving a balancedrelief valve assembly capable of maintaining anim creased pressure above Ltank pressure on the irltake'side ofthe engine-drivenfuelpump during normal operation, and capable ,of 'maintaining a higher .controlled pressure duringr emergency operation.

Other and further-objects oftheinvention Will be apparent to those "skilledfinthe art from Athe following Vdetailed description pof )the annexed sheetof drawings which, by'wayof preferred example Vonly,'illustrate one embodiment of the invention.

On the drawing: Y

Figure 1 is af -broken rvertical` 'cross-sectional view ofan wairplane fuertankhaving mounted In Figure 1 the reference numeral I0 indicates Vgenerally an airplane fuel tank Vented to the atmosphere as at Ilia. An lairplane engine II is.

equipped with an engine-driven fuel` pump I2 for supplying fuel under pressure through a dis-v charge line I3 to a fuel and air mixing device such as a carburetor I4 for the 'engineN II.' The` carburetor I4 discharges, as is customary, into the intake manifold I5 of the engine II.

A turbo-supercharger I5 discharges air under pressure'through a pipe I'I to the carburetor I4.` The fuel pump I2' includes a balanced relief valveassembly therein (not shown) subjected to the pressure in the intake manifold I5 through aline I 8. Alternatively, of course, the "line I8 could communicate with the discharge tube I1 of the 'supercharger I 6 In accordancewith this invention, afpositivedisplacement type booster pump is mounted in the bottom of the fuel tank I0 to receive fuel directly from the tank. The pump 29 has an inlet 2| communicating'with the bottom of the tank, so that fuelin the tank will drain directly` into the pump Awith a minimum .of restriction. Y'Ihe drawing illustrates the inlet 2l to be somewhat 'elevated above the bottom ofthe tank. "It should 'be understood that, in actual installations, the inlet 2l` will communicate with the very bottom of the tankandthe elevated positionof the pump 20j in V'the tank `,has been lillustratedl merelyV for the purpose of convenienceinV illustration ofthe various tubes in the system.

Thev particular pump 29 illustrated is of the sliding-vane typeincluding a sleeve 22 defining agjpumpbore 22d'with its inner surface andreceivingtherein a roto-r 23 carrying a plurality of sliding Avaries. 24 for `acting on ,theVV pump bore 22a. to propel fuel from the inlet 2I tothe outlet 25 of',.the pump. This outlet25 is connected through a pipe or tube 25a with`the intake side of the' engine-driven fuel pump I2,v i

I'he discharge side 25 of the pump 29 is adapted tocommunicate with the intake side 2IY of the pump through a relief valve` 26 to relieve eX- I that the pump 'does not supply suiiicient fuel `to the intake of the pump I2.l The by-pass valve `2.`I.is held in closed positionby a light spring 21a;

rThe relief valve 26 is urged to closed position by means of a coiled spring 28 mounted in a casing. u TheV compression of the'spring 28 can be ad- -justed by means of a control screw 29 which ,operates a top retainer 30 for the spring, to move this retainertoward and away from a bottom retainer SI for the spring. f

In order that the pressure of spring 28V wil1 be the sole, determining factor for the amount of fluid relieved from the discharge side of the pump, anpressure-balancing flexible diaphragm 32 is provided. Y'Ilhisdiaphragm 32 can be composed of synthetic rubber-impregnated flexible fabric. The diaphragm 32' separates a chamber 33 in the casing housing the spring 28 from a chamber 34 in the pump housing the reliefvalve 26. The

'diaphragm has me central portion thereof. iixed to the relief Valve 26 to move therewith, While the peripheral portion of the diaphragm can be clamped between casing sections, ofthepump.

The bottom of the diaphragm 32' is thus subjected toA pressure in the chamber 34, while the s; top of the diaphragm 32 is subjected to whatever base pressure exists in the spring chamber 33.

As shown in Figure 2, the pump 2U is driven by an electric motor35 energized from any suitable source of electric current, such as a battery B. lCurrent to the motor 35 from the battery B is controlled by a switch 36.

During normal operation, the pump 20 pumps excessive Yamounts of fuel into the discharge side 25 thereof, and the reliefvalve 2t is opened to recirculate the excess fuel back to the intake side 2| of the pump. The pressure maintained in the discharge side 25 of the pump will be controlled by the pressure of the spring 28, since this spring urges ,the relief valve 25 to closed position', and

the relief valve, by being subjected to pump dis-V charge pressure on the other side thereof is, of course, urged to open position by this discharge pressure. The diaphragm 32 Ais arranged forfof movement with the relief valve and has an effec# tive area on one side exposed to base pressure jin the spring chamber 33 balancedrby an equal valve area exposed to pump discharge pres`sure. In

addition the varea. `of the diaphragm 32 'exposed tions in inlet pressures and compensating variai tions in pump discharge and base pressures, so that the pump pressure'will be maintained at a pressure differential above the base pressure de-v termined solely by the spring.,

The chamber 33 communicates through a tube V3l with the bottom chamber 38a of a second relief valve assembly 38. This assembly includes an intermediate chamber 38h separated from the chamber'38arby a relief valve 39, and a top chamber 38e separated from the intermediate 'chamber 38h by a'flexible,'diaphragm` 4III) similar to: the

diaphragm 32. The relief ,Vall/,e l39 islconn'ected to the central portion ofthe diaphragmIl, and is spring-urged to closedposition by a coil spring 4L I in the top chamber 38o. The spring 4 I, similarto the spring 28, can be radjustably compressed by means `of an operating screw 42 so as to exert ,a desired pressure on the relief valve 39 through thevdiaphragm 40. i

The chamber 38h c ommunicates'with the interiolr of the tank II)` through a drain vline 43. l

The chamber '33e communicates ythrough a tube 44 with either the intake manifold I5 ofithe airplane engine II or with the ambient air surrounding the tank depending upon the position of a valve 45, The valve 45 is adaptedr to selectively connect the interior of the chamber 38e with either the ambient air or the intake manifold. Thus the chamber 38e can either besubjected to a base pressure, which is the ambient air pressure, or the engine intake manifold pressure.

The tube 31 has a branch tube 31a communieating with the middle compartment 45a of a positively-operated valve 46; The chamber 46a has a bottom port 41 joining it with a bottom chamber 4Gb. A port 48 joins thechamber .46a with a top chamber 46c. The chamber 461,); Comf municates with the interior of the tank through a drain line 49. The chamber 46c-is connected through-a tube 5l! with the fuel line 25a on the discharge side of thepump 2B. The tube 50 has ay restrictedintermediate portion 50a to-preventi excessive leakage of fuellfrom the line 25a',A into the compartmentltc, while at the same time subjecting the compartment 46c to the pressure eX- isting in the fuel line 25a.

Avalve 5lis provided for closing the portll'l,

anda-.second valvei52 isprovided for closingthe port 48. The 'valves 5l.A andf52iare secured on.A or

integral-with a shaft 53 i and are so positioned that i' the port 4l is closed whenthe port lliifisopened` and, when the port 46: is closed, the; portV 41:1 isA opened;

The shaftv 53 is connected toa solenoid'corec" surrounded by a solenoid coil 55. Asrillustrated,

the coil 55 is energized.: fromthe batteryir B? and a switch` 5l in the battery circuit t0 the coil 55 isclosed so` that, as illustrated in Figure l, the core 54 is in raised positiomto open the port 48: and `close theqport'l. A spring urges the; core 54. tomove the valve 52 to, closed position,- and'y the-.valve 5l toY open position, when the` coilli.

is,` dea-energized as, forA example, .when the switch 51 is open as shownpin FigureiZ.

When the solenoidcoil. 55 mda-energized', the chamber 33;' of thepumprZD, isventedto the4 interior; of-` thetank Nl 0 throughthe tube 3l", branch- 31a, open portA llf'lg.chamberiliib;` and drain line 4Q) The s base; pressure.: on the balancing mechanism for.: the: reliefi valvegZB `is thusthat pressure eX- isting; in the, tank il);A Under such operatingcon-- ditions,of l course,.the; port; 48 `is closed and the chamber33-is not. subjected` to pump discharge pressure through' the tube 5U." Under these cone ditions, the pumpf willdeliver` fuel atta constant pressure differentiaL abovethe base pressure ex` istinginfthe'interior'of'the tank depending upon the-settingofthe springL 28; The spring 28 is preferably. set so thatA the fuel? pressurein line 25a will be from seven to eight pounds persquare- Such pressures` arei sufficient to prevent liberation ofi gas andvapor' bubbles in the fuelline and'only fully liquidfuel .g

inch' above tank pressure:`

ispressured through thefuelY line 25a to thel intake side ofthev engine-driven fuel* pumpi2.-

Failurefof the system through vapor lockis thus prevented;

Under emergencyJ conditions,` however, suchL as"A f:

when the engine-driven pump` |2 fails, it is, desirable-to deliver fuel under higherfpressures to:

theline-ZEa. Unless'some means were provided` for changing the pressure ofi the spring 23v on the reliefvalve 26, or for adding to the eiTectof :f

this springy pressure on` the relief valve, the discharge pressure of the pump would remain the same.

In accordance with this inventionthe solenoidv valve 46 is energized, as by closing the switch til:`

to' open the port 48 and close the portl'l.` This vents discharge .pressure from the line 25a, through the tube 5i)` to the chamber t; and thencel through. the port 43. intoI the chamber 46a, branch tube 3'la,.and`tube 3l intothe spring.

chamber 33. As a resultpump discharge.A pres.- sure, isadded to., the spring pressure, in chamber` 33, and the relief valve is urged toward` closed.

positionwith an addediorce thereby` permitting the, building up. ofpressurein the line 25a.

This pressure would buildup to,the maximum:r

capacityr ofthe pump; or rupture ,point of the diaphragm 32, unless lsome means were provided for relieving the pressure. This means is provided in the second relief valve assembly 38 ation of the engine.

tially identical with the pump 23 and includes a` which comes into eifect to vent the chamber 331 to the relief valve 39 Whenever the chamber 33v is not vented tothe tank through the drain line 9; The relief valve 39 is adapted to beopened" by pressures' existing in the chamber 33 abovev pressures exertedon the relief valve 39 by the spring 4l and by the pressure in the compartment 38o. When opened, the valve 39 Willvent the chamber 33 to the interior of the tank through the drain line' 43.

The spring can be set to exert any desired .pressure on the valve 39 and the pressure in the chamber 38o can either be based on ambient air pressure surrounding the tank I0, or pressure in the intake manifold l5 of the engine Il. Therefore, the pressure in the chamber 33 is limitedby a second relief valve mechanism which is arranged to maintain a desired constant pressure differential above a base pressure (either ambient air pressure or intake manifold. pressure). Since-the ambient air pressure is substantially the same as that existing in the vented tank lli, except for a slight differential due to head of fuel in the tank, the base pressureon which the pump discharge pressure diierential is maintained can be the same, or` different, de:-

pending upon Whether or not the chamber 38cis vented to the atmosphere, or to the intake manifold pressure. In any event, the spring 4|' will be the sole determining factor for .mainteby-pass means so that fuel from. the line 25a can be by-passed around the pump into the'tubev If the; pump 2U becomes inoperative the'by-pass valve 2'1 is effective so that the pump I2 can always receive fuel from the tank.

It will, of course, be understoodY that various details of construction may be varied through* a Wide range-without departing from the principlesV of this invention and it is, therefore, nottthepurpose to limit the patent granted hereon other'- wise than necessitated by the scope of the appended claims.

I claim as my invention:

`l. Apparatus for maintainingr selected pump pressure differentials which comprises'a pump having a uid intake and aI fluid discharge' side,

a relief valve for relieving fluid from the discharge tothe intake sideofthe pump, spring-biased diaphragin means urging thevalve toward closed position for maintaining a selected pump discharge pressure, a positively' operated valvefor selectively subjecting said diaphragm-meansfto pump discharge pressure to` increase the relief; valve closing for-.ce` exerted. bysaid means and' create a dierent pump discharge pressure` dife ferential, and a second relief valve'f Cooperating,

with said positively operating valve for limiting said effect.

2. Apparatus for maintaining selected constant During emergency operation pressure differentials which comprises a pump havingan inletY and an outlet, a relief valve assembly for relieving fluid from the outlet to the inlet side of the pump, said assembly including pressure-balancing means subjected to an adjustable pressure on one side and the pump outlet pressure on the other side for maintaining `a predetermined pressure differential between the pressure in the pump outlet and said adjustable pressure, a second valve subjected to pump outlet pressure on one side and on the other side to the pump inlet pressure; means for operating'said second valve to subject said one side of the pressure-balancing means to pump outlet pressure, and a third valve including pressure-balancing means vented to the pump inlet pressure on one side and on the other side to said one side of the pressure-balancing means of the relief valve for relieving pressure on said one side of the pressure-balancing means of the relief valve when said one side is ventd to pump outlet pressure whereby said second valve can be operated to select constant pressure differentials of different values.

3. Apparatus for maintaining selected pressure differentials which comprises a pump having `a pressure-balanced relief valve assembly capable of being set to maintain a constant pressure differential between the two sides of the valve, means for selectively subjecting one side or both sides of the' pressure-balanced relief valve to pump discharge pressure, and a second relief valve effective to vent one side of the pressure-balanced relief valve of the pump to a predetermined pressure whenever said one side of the balanced relief valve is subjected to pump discharge pressure for relieving said pump pressure.

4. A fluid pressure control apparatus comprising a fluid transfer mechanism having an intake and an outlet side, a spring-pressed relief valve adapted to relieve excess pressures from the discharge to the intake side of said mechanism, a pressure-balancing device cooperating with said valve subjected to discharge pressure on one side and ambient air pressure on the other side to cooperate with said spring for maintaining the discharge pressure'at a constant pressure olif- Vferential above the ambient air pressure, a positively-operated valve for subjecting the balancing device to pump discharge pressure instead of ambient air pressure, and a relief mechanism adapted to relieve excess pump pressures on said balancing device for maintaining a different con-l stant pressure differential above the ambient pressure on`the discharge side of said mechanism.

Pumping apparatus comprising a positive displacement pump having an inlet and an outlet, a relief valve for venting the outlet with the inlet to relieve excess pressures, means on said pump defining a spring chamber, a flexible diaphragm separating said chamber from said pump, a spring in said chamber acting on one side of said diaphragm, said relief valve acting on the other side of said diaphragm, a positively-operated valve having three chambers connected through ports, a double-acting valve head in said valve for simultaneously opening one of said ports Ywhile closing the other of said ports, means for venting one of said chambers in the valve to pressure in the spring chamber, means for venting an adjacent chamber in the valve to pump 8 discharge pressure, means for venting the third chamber in the valve to tank pressure whereby said valve can be actuated'to move the valve head for subjecting the spring chamber to tank pressure or to pump discharge pressure, and a second relief valve mechanism operativev forrelieving excess pump pressures from the spring` chamber. f

6. Pumppressure control apparatus comprising a pump having a relief valve normally subjected to pump discharge pressure on one side and a predetermined constant but adjustable pressure on the other side, and means for selectively adding pump discharge pressure to said other side of the relief valve to increase the discharge pressure to greater than said predetermined value.

7. Pump pressure control apparatus comprising a pump having a relief valve normally subjected to pump pressure on one side and ambient plus spring pressure on the other side, a solenoid operated valve for adding pumpdischarge pressure to said other side of theV relief valve, and a second relief valve `for relieving eX- cessive pump pressures from said other side of the first mentioned relief valve.

8. A uid pressure control apparatus comprising a pump having fluid intake and discharge sides, a pressure balanced relief valve for relieving excess pressures from the discharge side of the pump, said relief valve including an operating diaphragm having at one side a pressure` chamber enclosing aV spring for normally biasing said relief valve to closed position, both sides of said diaphragm being normally vented `to the pressure at the intake side of said pump, a positively operated valve for connecting said pressure chamber to the discharge side of said pump to urge the relief valve toward closed position with greater force, whereby said relief valve will maintain an increased pressure differential' on the discharge side of the pump, and means for relieving excess pump pressure from said relief .valve whenever said positively operated valve effects said increase pressure differential.

9. A fluid pressure control apparatus comprising fluid transfer means having intake and discharge sides, a spring pressed relief valve for relieving fluid from the discharge to the intake side of said fluid discharge means, aV flexible'diaphragm operatively connected to said reliefvalve and having both the spring opposing` side and the spring aiding side thereof normally exposed to a base fluid pressure, and means for selectively increasing the fluid pressure on the spring aiding side of said diaphragm to Vincrease the discharge pressure of Vsaid transfer means.' V, Y

10. A fluid pressure control apparatus comprising a pump having fluid intake and discharge sides, a relief valve in said pump for release` of fuel from said discharge to said intake side of the pump, spring means urging said relief valve tov its closed position, a balancing device connected to said relief valve, both sides ofsaid balancing device being normally vented to the pressure at the intake side o-f said pump, whereby said relief valve maintains a constant pump' discharge pressurel differential above intake pressure; and means for selectively subjecting said spring aiding side of said balancing device to pump discharge pressure Vfor increasing the pump .dis-

charge pressure differential. Y s

RUSSELL R. CURTIS. c 

